The invention relates to improved high frequency hetrodyne receivers. More particularly, the invention relates to the use of a GaAs (gallium arsenide) FET as a pre-amplifier in a high frequency receiver. The beneficial use of the special properties of a GaAs FET allows the realization of a receiver front end without a circulator and a notch filter.
Traditionally, the front end of a high frequency receiver, particularly a hetrodyne microwave receiver, required both a circulator and a notch filter. These two devices required custom tuning which complicated production and installation of the receiver front end. In addition, the circulator and notch filter represent an obvious additional expense in comparison to the receiver front end of the invention which requires neither devices.
Therefore, it is an object of the invention to provide a high frequency receiver which does not require a circulator or a notch filter.
It is also an object of the invention to provide a high frequency hetrodyne receiver configuration which allows the preselector filter to provide both a bandpass function and an image frequency notch function when used with a preamplifier before the mixer.
Finally, it is an object of the invention to provide a high frequency hetrodyne receiver of reduced complexity and reduced cost that utilizes a GaAs FET preamplifier.